We are investigating the structural basis and functional expression forms of glyceraldehyde-3-phosphate dehydrogenase in mammalian skeletal muscle. In particular, do these forms represent conformational isomerism, posttranslational modification, or duplication and mutation of the structural gene? When do these forms occur in development and to what extent are their distributions tissue specific? Is the heterogeniety expressed in an identifiable way in the catalytic properties of the enzyme or as steps in the intracellular protein turnover? In a second part of this project, we are examining factors which affect the concentration level of glycogen phosphorylast protein and related enzymes of glycogen metabolism in liver. BIBLIOGRAPHIC REFERENCE: H. P. Jennissen, W. H. Horl, U. Groschel-Steevart, S. F. Velick, and L. M. G. Heilmeyer, Jr., Localization and Turnover of Phosphorylase Kinase in Rabbit Skeletal Muscle, in Metabolic Interconversion of Enzymes, Proceedings of the 4th International Symposium, Arad, Israel, 1975. In press.